Adenomatous polyposis coli (APC), the putative gatekeeper of colorectal carcinogenesis, is mutated in approximately 80% of sporadic colon tumors and provides the molecular basis for the familial adenomatous polyposis (FAP) syndrome. Dysfunctional APC/(-catenin signaling, is also an important event in some sporadic human cancers, including prostate, ovarian, pancreas, liver, and skin. Thus, the APC/beta-catenin pathway represents an important target for chemopreventive intervention. Preclinical studies have repeatedly documented the antitumor activity of perillyl alcohol (POH) and support its further development as a chemopreventive agent. While the findings from these studies continue to be promising, our understanding of the mechanism of action of POH remains very limited. Elucidation of the biochemical and molecular pathways altered by POH will facilitate both the identification of biomarkers of POH activity and the development of structurally related compounds that may be more efficacious in preventing tumor formation. The hypothesis of the proposed experimentation is that POH induces apoptosis by decreasing both nuclear levels of beta-catenin and the transcriptional activation of genes that are downstream targets of the APC/beta-catenin pathway. Support for this hypothesis is provided by published and preliminary data, which suggest that POH can modulate both beta-catenin and its downstream target cyclin D1. Six human cell lines bearing defined mutations in APC or beta-catenin will be utilized in the proposed studies. The effect of POH on the transcription, translocation and functional interaction of APC, beta-catenin, GSK3beta, Axin, casein kinase 1, E-cadherin and p120 catenin will be determined. The ability of POH to modulate downstream targets of the APC pathway will also be evaluated. Results from the proposed research will determine the feasibility of developing POH as a chemopreventive agent for patients with colorectal cancer and provide the basis for future R01 funding.